The purpose of this study was to evaluate the shape and impacted pattern of mesiodens and associated complications using three dimensional images produced by dental CBCT. This study was based on the CBCT (CB Mercury, Hitachi, Tokyo, Japan) radiographic view of 280 pediatric patients who visited the Department of Pediatric Dentistry at the Chosun University Dental Hospital with the chief complain of mesiodens during between 2007 and 2012. Impacted mesiodens occurs more frequently in boys than in girls, the ratio being approximately 3.3:1 and most cases were observed between 6 and 8 years of age. The number of mesiodens per patient was 1.38. Majority of the mesiodens were conical (79.5%) in shape and inverted (48.6%) in direction. The mesio-distal position of mesiodens were the most common in middle sector (81.8%), vertical level were the most common near cervical (60.3%), and labio-palatal position were the most common at palatal side of the dental arch (73.8%). 47.5% of mesiodens had complications and common complications associated with mesiodens were displaced tooth and delayed eruptions. The shape, vertical level, and labio-palatal position of mesiodens had correlations with complications. CBCT appears to be an excellent diagnostic tool, providing three dimensional information and accurate images, for diagnosis of impacted mesiodens.

The aim of this study was to evaluate changes in demineralization resistance and bonding strength of light cured glass ionomer after the addition of nano hydroxyapatite in various ratios. Fuji II LC GIC (GC Co., Japan) was used as the control group and also as a base material for experimental group. HA was mixed into the RMGIC at various ratio to create a HA-LC GIC mixture, preparing six experimental groups, i.e. 5%, 10%, 15%, 20%, 25%, 30% HA-LC GIC. According to the results, the bonding strength increased due to the addition of HA, showing the maximum value at the 15% nano HA group (p < 0.05). Under CLSM observation after 4 days of demineralization, the HA groups were more resistant to demineralization compared to the control group. No significant difference was observed between HA groups. In analysis through SEM, the HA groups showed attachment of granular materials and decreased demineralized tooth surfaces under influence of HA particles.

The aim of this study was to evaluate the acid neutralizing capacity and to observe surface changes of giomer in comparison with composite resin, when it comes in contact with an acidic solution. A packable giomer(Beautifil II) and a flowable giomer(Beautifil Flow F02) were used as experimental groups, while a packable composite resin( Z-250) was used as control group. pH values were measured after mixing the specimens of the disc and powder types with a pH 2.0 hydrochloric acid solution, respectively. Also, in the case of powder type giomers used in the earlier experiment, their pH values were measured again after mixing them with a fresh acid solution. Moreover, surface structure changes of disc type specimens were observed by using a scanning electron microscopy(SEM). In the disc type test, the pH values of packable giomer were significantly increased after 24 hours(p < 0.05). In contrast, in the powder type test, the pH values of packable and flowable giomers were dramatically increased within 30 minutes. The pH value of packable giomer, in particular, was higer than that of flowable giomer(p < 0.05). In the repeated neutralizing test, the degree of pH variation was lower than that of the previous neutralizing test(p < 0.05). Erosive changes on the surface of packable giomer were observed to be more than those on composite resin and flowable giomer as well. In conclusion, giomer has a acid neutralizing capacity, when it comes in contact with an acidic solution. Especially, packable giomer with high filler content has a greater acid neutralizing capacity than flowable giomer.

Calcium hydroxide mixture medicaments can nearly be considered to be the ideal primary tooth filling material. However, long-term application of calcium hydroxide combinations as an intra canal medicament softens dentin. The aim of this study was to evaluate the effect of calcium hydroxide on the microhardness of root dentin of primary tooth. For the study, 60 extractedprimary incisors were divided into 3 groups (no medicament, calcium hydroxide/iodorform mixture, and calcium hydroxide/distilled water mixture). After the cleansing and shaping of canals, calcium hydroxide medicaments were applied and stored for different periods of time (1, 7, 30, 90 days). The root was horizontally sectioned into 2 mm thick specimens and the microhardness was measured using Vickers microhardness tester. The results were as follows : Root dentin microhardness of primary teeth decreased with long term exposure to calcium hydroxide medicaments according to the experimental period and showed statistically significance (p < 0.05). Root dentin microhardness of primary tooth filled with calcium hydroxide mixed with distilled water showed more decrease than filled with Vitapex and showed statistically significance (p < 0.05). Root dentin microhardness of a control group without exposure to calcium hydroxide decreased according to the experimental period and showed statistically significance (p < 0.05).

Mineral trioxide aggregate (MTA) has recently been used as a pulpotomy medicament for primary molars. The aim of this study was to evaluate and compare the proliferation and differentiation potential of dental pulp stromal cells of permanent teeth and deciduous teeth cultured on MTA-coated surface. Human dental pulp stromal cells were obtained from human permanent premolars and deciduous teeth and cultured on MTA-coated culture plates. The cells were subjected to proliferation assay and cell cycle analysis. Their differentiation potential was evaluated by analysing changes in the mRNA expressions of runt-related transcriptional factor 2 (Runx2) and alkaline phosphatase (ALP). Morphological changes of cells in direct contact with MTA were observed using scanning electron microscopy (SEM). The proliferation rates, distribution of cell cycles and mRNA expression patterns of Runx2 and ALP were similar in both types of pulpal cells. SEM observations revealed that both types changed into more dendrite-like cells. On the surface of MTA, human dental pulp stromal cells from deciduous and permanent teeth were able to both proliferate and differentiate into cells that induce mineralization. MTA is suitable as a biocompatible pulpotomy medicament for primary teeth.

Although the first case of supernumerary teeth had been documented almost 20 centuries ago, the etiology of supernumerary teeth still remains unclear. The prevalence of supernumerary teeth in the general Asian population is between 2.7% and 3.4%. The pathogenesis of supernumerary teeth has been attributed to phylogenetic reversion(atavism), splitting of the tooth bud(dichotomy theory), locally induced hyperactivity of the dental lamina and a combination of genetic and environmental factors(unified etiologic explanation). This report describes 3 cases of monozygotic twins with mesiodens who visited the pediatric dental clinic of Kyungpook national university hospital, and this is significant to support genetic factors involoved in the development of supernumerary teeth.

Cleft lip and palate, the most common craniofacial anomalies, are severe congenital defects that have an incidence of 0.28 to 3.74 per 1000 live births. Although there has been great improvement in the field of cleft surgery, surgical approach cannot be the single solution to resolve the various problems encountered in patients with cleft lip and palate. The concept of presurgical infant orthopedics (PSIO) for gradual closure of the cleft gap and simplified surgical performance was first introduced by McNeil in 1950. Recently, there are many attempts not only to approximate the alveolar segments but also to reshape the nasal cartilage. Three infants with unilateral cleft lip and palate were referred from the department of Plastic Surgery for presurgical nasoalveolar molding (PNAM). Maxillary appliances using resin with orthodontic wire were fabricated. Then these appliance was applied until patients underwent lip surgery. In all cases, the patients could wear the appliance all day since they were able to eat even with the appliance on, This resulted in significant improvements in the nasal symmetry were found. Our appliance, namely K-NAM, extends the wearing time within the limited period and as a result it is expected to maximize the treatment effects. Used properly, this appliance would play a major role in enhancing nasal symmetry with satisfactory results.

Paradigm shift in management of infected immature permanent teeth has occurred. The new concept of the treatment includes minimal or no intracanal instrumentation, disinfection with triple antibiotic paste and sealing with mineral trioxide aggregate. This regenerative endodontic treatment promotes differentiation of periradicular stem cells that induce regeneration of vital tissue and continuation of root formation. Thorough disinfection and three-dimensional scaffold are important in this new concept of the treatment. Platelet-rich fibrin has been reported as `new scaffold` instead of blood clot, which had been used in the past. Triple antibiotics can be used to disinfect the tooth but may lead to complications including discoloration. Three cases of infected immature permanent tooth caused by dens evaginatus fracture are presented. After removal of necrotic pulp and thorough intracanal irrigation, only platelet-rich fibrin was applied to the root canal in the first case. In the other cases, topical antibiotics was used for disinfection and platelet-rich fibrin for scaffold. In all the cases, the opening was sealed with mineral trioxide aggregate. All the cases showed proper healing of inrabony lesion and some lengthening of root. According to these cases, regenerating vital tissue of the infected immature permanent tooth can be achieved with disinfection and application of platelet-rich fibrin.

There are many problems in evaluating study results by p value in null hypothesis testing for dental research. It is a logical fallacy to conclude that the null hypothesis is true when the it is not rejected. There are much serious misunderstanding about p value, and researchers should be cautious about interpreting p value in writing papers. As alternatives to complement or replace the null hypothesis significance testing, effect size, confidence interval, and Bayesian statistics are introduced.